جذب و واجذب كادميوم از محلول هاي آبي توسط زئوليت طبيعي، اصلاح شده با پلي اكريل آميد و نانو زئوليت

چكيده انگليسي :

83 Sorption and Desorption of Cadmium from Aqueous Solutions by Natural Polyacrylamide Modified and Nano zeolite Farnaz Alsadat Hodaee Koshkoee f hodaee@ag iut ac ir Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisors H Shariatmadari E mail address shariat@cc iut ac ir M Hamidpour E mail address mohsenhamidpour@yahoo comAbstract Cadmium as a heavy metal is one of the most important environmental pollutants Due to the longhalf life and high toxicity of cadmium for human and animals this element is of special importance Cad mium pollution of water resources due to its direct role in production of agricultural crops and foods isvery dangerous Industrial development has led to increased heavy metal pollution in environment endan gering human health On the other hand due to the shortage of water resources and the necessity of se wages use investigation on finding and synthesis of high efficient sorbents is crucial In addition to highefficiency the sorbents should be affordable with low cost Natural clays due to environmental sustaina bility abundance low cast and high surface area are currently the most widely used sorbents for heavymetals removal processes In recent years nano materials with larger sorptive surface area and faster sorp tion kinetics are used for elimination of water pollutions Better understanding of the adsorption and de sorption of heavy metals and the effects of ionic strength and the pH of solution is needed for effectivepurification of waters contaminated with heavy metals In this study the natural zeolite nano zeolite andpolyacrylamid modified zeolite are examined for sorption of cadmium from aqueous solutions The natu ral clay was obtained from Firoozkooh mine and the other sorbents were prepared from the natural sam ple The sorbents were analyzed for some chemical and physical properties such as elemental composi tion cation exchange capacity point of zero charge and the XRD diffraction The X ray diffraction pat terns showed a shift from crystalline to amorphous phase in nano zeolit but in the case of the modifiedclay there was no change in the mineral structure The kinetics of sorption examined at 10 mg l of cad mium concentration and 0 5 to 24 hrs of reaction time Using different kinetics models the best fits wereobserved by the pseudo first order and pseudo second order models for the modified zeolite and Elovichand power function for zeolite and nano zolite Sorption isotherms were derived at the concentrationranges of 1 to 10 mg l as low and 5 to 100 mg l as high concentration in a 24h batch equilibrium experi ment Desorption of Cd II was also studied with the clay samples initially treated with the metal concen trations of 4 5 10 45 and 100 mg l during the sorption study Sorption isotherms of Cd were well de scribed by the Freundlich and Coble Korrigan models Desorption isotherms of Cd from zeolite in lowconcentration showed little deviation from sorption data indicating a reversible sorption But for othersorbents noticeable hysteresis was observed in all sorbate concentrations The effect of ionic strengths of0 01 and 0 1 molar on sorption were also examined at Cd concentrations of 4 5 and 45 mg l The increasein ionic strength decreased the sorption specially at higher Cd concentration This effect was differentamong the sorbents and nano zeolite showed the list decrease in sorption under elevated ionic strength The effect of initial pH of 5 to 7 on sorption was also examined The Cd sorption decreased with decreasein pH for all sorbents This effect was the list in modified zeolite Key words Cadmium sorptionu Cadmium desorption Natural zeolite Nano zeolite Modifiedzeolite Polyacrylamide

هدائي كشكوئي، فرناز السادات

جذب و واجذب كادميوم از محلول هاي آبي توسط زئوليت طبيعي، اصلاح شده با پلي اكريل آميد و نانو زئوليت

زئوليت اصلاح شده